As a method of measuring a target substance (a trace component or the like) contained in a biological sample, an immunological measuring method utilizing an antigen-antibody reaction is widely used, and radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), or the like are known. Recently, serum or plasma is used as a sample in many cases, but a measuring method in which whole blood can be measured without pretreatment is desired due to pretreatment hassle. However, since a whole blood sample contains not only a trace component or the like as a subject to be measured, but also many contaminants (non-target substances), it cannot be carried out in the same manner as conditions using serum samples or plasma samples in many cases. In order to improve the reaction precision, it has been reported, as shown in Patent literature 1, that prozone can be avoided by adding a reaction inhibitor (a free antibody or its fragment capable of competing with an antibody immobilized on a solid phase or a labeling substance) in a reaction. In this case, a plurality of reaction substances co-exist in a single measurement, and therefore, it is difficult to construct a measurement system.
Further, as a technique capable of conveniently examining a plurality of samples, various automated immunologically measuring apparatus are known, such as an automated measuring apparatus capable of simultaneously measuring a plurality of samples, as shown in Patent literature 2. It is disclosed that, in this automated measuring apparatus, samples containing a target substance are dispensed into a cartridge having a dilution well where a predetermined sample amount is diluted into a desired dilution rate, a reaction well where a target substance contained in the samples is reacted with a substance which specifically reacts with it, and a storage well containing reaction components or the like; the samples are diluted to desired dilution rates on the cartridge; the target substance contained in the diluted samples is reacted with the substance which specifically reacts with the target; and the amount of the resulting reaction product is measured, to conveniently measure a plurality of target substances with different dilution rates contained in the samples. It is also disclosed that the apparatus has an aspirating and discharging unit, and the dispensing step and measurement are carried out using this unit.
On the other hand, as a method of measuring a whole blood sample as a subject, a method in which a surfactant is contained to avoid the effects of components contained in whole blood samples is disclosed, as shown in Patent literature 3. However, in the measuring method in which each reaction reagent is sequentially dispensed to carry out reactions, it is not known that the divergence between plasma and whole blood derived from the same sample is observed, and a method to solve such problems has not been proposed.